diff options
Diffstat (limited to 'sdk-modifications/libsrc/fs/file_allocation_table.c')
| -rw-r--r-- | sdk-modifications/libsrc/fs/file_allocation_table.c | 330 |
1 files changed, 330 insertions, 0 deletions
diff --git a/sdk-modifications/libsrc/fs/file_allocation_table.c b/sdk-modifications/libsrc/fs/file_allocation_table.c new file mode 100644 index 0000000..f382b52 --- /dev/null +++ b/sdk-modifications/libsrc/fs/file_allocation_table.c @@ -0,0 +1,330 @@ +/* + file_allocation_table.c + Reading, writing and manipulation of the FAT structure on + a FAT partition + + Copyright (c) 2006 Michael "Chishm" Chisholm + + Redistribution and use in source and binary forms, with or without modification, + are permitted provided that the following conditions are met: + + 1. Redistributions of source code must retain the above copyright notice, + this list of conditions and the following disclaimer. + 2. Redistributions in binary form must reproduce the above copyright notice, + this list of conditions and the following disclaimer in the documentation and/or + other materials provided with the distribution. + 3. The name of the author may not be used to endorse or promote products derived + from this software without specific prior written permission. + + THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED + WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY + AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE + LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; + LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, + EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + + 2006-07-11 - Chishm + * Original release + + 2006-07-11 - Chishm + * Made several fixes related to free clusters, thanks to Loopy + + 2006-10-01 - Chishm + * Added _FAT_fat_linkFreeClusterCleared to clear a cluster when it is allocated +*/ + + +#include "file_allocation_table.h" +#include "partition.h" +#include <string.h> + +/* +Gets the cluster linked from input cluster +*/ +u32 _FAT_fat_nextCluster(PARTITION* partition, u32 cluster) +{ + u32 nextCluster = CLUSTER_FREE; + u32 sector; + int offset; + + switch (partition->filesysType) + { + case FS_UNKNOWN: + nextCluster = CLUSTER_FREE; + break; + + case FS_FAT12: + sector = partition->fat.fatStart + (((cluster * 3) / 2) / BYTES_PER_READ); + offset = ((cluster * 3) / 2) % BYTES_PER_READ; + + + _FAT_cache_readPartialSector (partition->cache, &nextCluster, sector, offset, sizeof(u8)); + + offset++; + + if (offset >= BYTES_PER_READ) { + offset = 0; + sector++; + } + + _FAT_cache_readPartialSector (partition->cache, ((u8*)&nextCluster) + sizeof(u8), sector, offset, sizeof(u8)); + + if (cluster & 0x01) { + nextCluster = nextCluster >> 4; + } else { + nextCluster &= 0x0FFF; + } + + if (nextCluster >= 0x0FF7) + { + nextCluster = CLUSTER_EOF; + } + + break; + + case FS_FAT16: + sector = partition->fat.fatStart + ((cluster << 1) / BYTES_PER_READ); + offset = (cluster % (BYTES_PER_READ >> 1)) << 1; + + _FAT_cache_readPartialSector (partition->cache, &nextCluster, sector, offset, sizeof(u16)); + + if (nextCluster >= 0xFFF7) + { + nextCluster = CLUSTER_EOF; + } + break; + + case FS_FAT32: + sector = partition->fat.fatStart + ((cluster << 2) / BYTES_PER_READ); + offset = (cluster % (BYTES_PER_READ >> 2)) << 2; + + _FAT_cache_readPartialSector (partition->cache, &nextCluster, sector, offset, sizeof(u32)); + + if (nextCluster >= 0x0FFFFFF7) + { + nextCluster = CLUSTER_EOF; + } + break; + + default: + nextCluster = CLUSTER_FREE; + break; + } + + return nextCluster; +} + +/* +writes value into the correct offset within a partition's FAT, based +on the cluster number. +*/ +static bool _FAT_fat_writeFatEntry (PARTITION* partition, u32 cluster, u32 value) { + u32 sector; + int offset; + u8 oldValue; + + if ((cluster < 0x0002) || (cluster > partition->fat.lastCluster)) + { + return false; + } + + switch (partition->filesysType) + { + case FS_UNKNOWN: + return false; + break; + + case FS_FAT12: + sector = partition->fat.fatStart + (((cluster * 3) / 2) / BYTES_PER_READ); + offset = ((cluster * 3) / 2) % BYTES_PER_READ; + + if (cluster & 0x01) { + + _FAT_cache_readPartialSector (partition->cache, &oldValue, sector, offset, sizeof(u8)); + + value = (value << 4) | (oldValue & 0x0F); + + _FAT_cache_writePartialSector (partition->cache, &value, sector, offset, sizeof(u8)); + + offset++; + if (offset >= BYTES_PER_READ) { + offset = 0; + sector++; + } + + _FAT_cache_writePartialSector (partition->cache, ((u8*)&value) + sizeof(u8), sector, offset, sizeof(u8)); + + } else { + + _FAT_cache_writePartialSector (partition->cache, &value, sector, offset, sizeof(u8)); + + offset++; + if (offset >= BYTES_PER_READ) { + offset = 0; + sector++; + } + + _FAT_cache_readPartialSector (partition->cache, &oldValue, sector, offset, sizeof(u8)); + + value = ((value >> 8) & 0x0F) | (oldValue & 0xF0); + + _FAT_cache_writePartialSector (partition->cache, &value, sector, offset, sizeof(u8)); + } + + break; + + case FS_FAT16: + sector = partition->fat.fatStart + ((cluster << 1) / BYTES_PER_READ); + offset = (cluster % (BYTES_PER_READ >> 1)) << 1; + + _FAT_cache_writePartialSector (partition->cache, &value, sector, offset, sizeof(u16)); + + break; + + case FS_FAT32: + sector = partition->fat.fatStart + ((cluster << 2) / BYTES_PER_READ); + offset = (cluster % (BYTES_PER_READ >> 2)) << 2; + + _FAT_cache_writePartialSector (partition->cache, &value, sector, offset, sizeof(u32)); + + break; + + default: + return false; + break; + } + + return true; +} + +/*----------------------------------------------------------------- +gets the first available free cluster, sets it +to end of file, links the input cluster to it then returns the +cluster number +If an error occurs, return CLUSTER_FREE +-----------------------------------------------------------------*/ +u32 _FAT_fat_linkFreeCluster(PARTITION* partition, u32 cluster) { + u32 firstFree; + u32 curLink; + u32 lastCluster; + bool loopedAroundFAT = false; + + lastCluster = partition->fat.lastCluster; + + if (cluster > lastCluster) { + return CLUSTER_FREE; + } + + // Check if the cluster already has a link, and return it if so + curLink = _FAT_fat_nextCluster(partition, cluster); + if ((curLink >= CLUSTER_FIRST) && (curLink <= lastCluster)) { + return curLink; // Return the current link - don't allocate a new one + } + + // Get a free cluster + firstFree = partition->fat.firstFree; + // Start at first valid cluster + if (firstFree < CLUSTER_FIRST) { + firstFree = CLUSTER_FIRST; + } + + // Search until a free cluster is found + while (_FAT_fat_nextCluster(partition, firstFree) != CLUSTER_FREE) { + firstFree++; + if (firstFree > lastCluster) { + if (loopedAroundFAT) { + // If couldn't get a free cluster then return, saying this fact + partition->fat.firstFree = firstFree; + return CLUSTER_FREE; + } else { + // Try looping back to the beginning of the FAT + // This was suggested by loopy + firstFree = CLUSTER_FIRST; + loopedAroundFAT = true; + } + } + } + partition->fat.firstFree = firstFree; + + if ((cluster >= CLUSTER_FIRST) && (cluster < lastCluster)) + { + // Update the linked from FAT entry + _FAT_fat_writeFatEntry (partition, cluster, firstFree); + } + // Create the linked to FAT entry + _FAT_fat_writeFatEntry (partition, firstFree, CLUSTER_EOF); + + return firstFree; +} + +/*----------------------------------------------------------------- +gets the first available free cluster, sets it +to end of file, links the input cluster to it, clears the new +cluster to 0 valued bytes, then returns the cluster number +If an error occurs, return CLUSTER_FREE +-----------------------------------------------------------------*/ +u32 _FAT_fat_linkFreeClusterCleared (PARTITION* partition, u32 cluster) { + u32 newCluster; + int i; + u8 emptySector[BYTES_PER_READ]; + + // Link the cluster + newCluster = _FAT_fat_linkFreeCluster(partition, cluster); + if (newCluster == CLUSTER_FREE) { + return CLUSTER_FREE; + } + + // Clear all the sectors within the cluster + memset (emptySector, 0, BYTES_PER_READ); + for (i = 0; i < partition->sectorsPerCluster; i++) { + _FAT_disc_writeSectors (partition->disc, + _FAT_fat_clusterToSector (partition, newCluster) + i, + 1, emptySector); + } + + return newCluster; +} + + +/*----------------------------------------------------------------- +_FAT_fat_clearLinks +frees any cluster used by a file +-----------------------------------------------------------------*/ +bool _FAT_fat_clearLinks (PARTITION* partition, u32 cluster) { + u32 nextCluster; + + if ((cluster < 0x0002) || (cluster > partition->fat.lastCluster)) + return false; + + // If this clears up more space in the FAT before the current free pointer, move it backwards + if (cluster < partition->fat.firstFree) { + partition->fat.firstFree = cluster; + } + + while ((cluster != CLUSTER_EOF) && (cluster != CLUSTER_FREE)) { + // Store next cluster before erasing the link + nextCluster = _FAT_fat_nextCluster (partition, cluster); + + // Erase the link + _FAT_fat_writeFatEntry (partition, cluster, CLUSTER_FREE); + + // Move onto next cluster + cluster = nextCluster; + } + + return true; +} + +/*----------------------------------------------------------------- +_FAT_fat_lastCluster +Trace the cluster links until the last one is found +-----------------------------------------------------------------*/ +u32 _FAT_fat_lastCluster (PARTITION* partition, u32 cluster) { + while ((_FAT_fat_nextCluster(partition, cluster) != CLUSTER_FREE) && (_FAT_fat_nextCluster(partition, cluster) != CLUSTER_EOF)) { + cluster = _FAT_fat_nextCluster(partition, cluster); + } + return cluster; +} |